An inkjet-type recording head is known as a liquid drop ejecting head for ejecting liquid drops from a plurality of nozzles. In such a recording head, it is required to reduce the whole size, even when complicate ink flow paths are necessary for the inside thereof in order to distribute and eject ink supplied from an ink supply source to the nozzles. Therefore, for example, JP-A-2006-334797 describes a small recording head formed by laminating a plurality of thin plates, each formed with penetration portions and concave portions, to form complicate ink flow paths inside.
The laminated plates includes a plurality of plates such as a nozzle plate where plural nozzles are formed in a hole shape and are arranged in a linear shape as a whole, a manifold plate where a long hole (opening) for forming a common ink chamber (a manifold) is formed in a through-hole shape, and a cavity plate where a pressure chamber receiving an ejecting pressure from an actuator is formed. The ink supplied from an ink supply source flows from the common ink chamber to the pressure chamber and the nozzle through the ink flow path in each plate.
Since the common ink chamber serves as a part for storing ink, which is distributed to the plural nozzles (see FIG. 6 in JP-A-2006-334797), it is necessary to form the common ink chamber so as to have a length substantially equal to a length of a nozzle row and a large inner capacity. In JP-A-2006-334797, the common ink chamber is formed by laminating two manifold plates, each of which includes long penetrating holes having the same shape, and sandwiching the manifold plates with an upper plate formed as a ceiling face of the common ink chamber and a lower plate formed as a bottom face thereof.
In JP-A-2006-334797, five nozzle rows are arranged so as to correspond to inks having four colors of black, magenta, yellow, and cyan (two rows are used for only the black ink). Hence, five rows of the common ink chambers are also arranged so as to correspond to the five nozzle rows. Therefore, each of the manifold plates includes five long penetrating holes arranged in substantially parallel.
However, for responding to a recent demand for increasing accuracy and speed of recording, a recording head is required to have increased number of nozzles and to employ increased number of colors. Therefore, the number of nozzles or the number of nozzle rows tends to increase. When the number of nozzle rows increases, the number of common ink chambers corresponding thereto also increases, and thus the number of long penetrating holes formed in the manifold plates also increases. In other words, cut-out portions (void portions) penetrating through the manifold plates increases.
However, it is difficult to increase a size of the manifold plates in order to avoid an increase in size of a recording head including the manifold plates. Thus, the frame portions remaining in the manifold plate have to be decreased according to an increase in number of the common ink chambers. Particularly, between the long holes for the common ink chambers adjacent to each other, a frame portion remains, which has a narrow width and elongates along the common ink chambers (the long holes) so as to have a length equal to that of the common ink chamber. For example, since the recording head described in JP-A-2006-334797 has five common ink chambers, five long penetrating holes are formed at the center portion of the manifold plate. Thus, only long four frame portions remain, which have a narrow width formed between the five long holes and elongate in substantially parallel to each other. Therefore, rigidity of the entire manifold plates remarkably deteriorates. Additionally, at the time of dealing with the manifold plates, the frame portions having a narrow width could bend downwardly.
For plates includes a frame portion having small area as described above, operability (handling ability) is poor in various processes such as parts inspection, parts packing, and assembly, and thus there has been a problem that it is easy to cause deformation and damage in the plates.